Optimal choice of measurement points in near field: numerical results

2018 ◽  
Author(s):  
Maria Antonia Maisto ◽  
Raffaele Solimene ◽  
Rocco Pierri
Keyword(s):  
Near Field ◽  
Optimal Choice ◽  
Numerical Results

RADIATED ACOUSTIC PRESSURE FROM A MOVING, NONUNIFORMLY VIBRATING CYLINDER WITH TWO SPHERICAL ENDCAPS

1994 ◽  
Vol 02 (01) ◽  
pp. 71-82 ◽  
Author(s):  
ZHAOXI WANG ◽  
SEAN F. WU
Keyword(s):  
Near Field ◽  
Translational Motion ◽  
Normal Component ◽  
Forward Direction ◽  
Numerical Results ◽  
Surface Velocity ◽  
Reverse Direction ◽  
Far Field ◽  
Field Source ◽  
Sound Diffraction

This paper presents numerical results of radiated acoustic pressures from a moving, nonuniformly vibrating cylinder with two spherical endcaps, based on an extended Kirchhoff integral formulation. Specifically, we consider cases in which the normal component of the surface velocity is nonzero on a portion of the surface, and zero elsewhere. Numerical results demonstrate that the radiation patterns depend critically on the frequency and source dimensions. For a noncompact source, the strongest radiation may not necessarily stem from a vibrating surface, but rather from a nonvibrating surface due to the effect of sound diffraction. The more noncompact the source is, the larger the number of side lobes in the near field and the more concentrated these side lobes will be. In the far field, however, the side lobes become smeared and less distinguishable. In other words, the effect of sound diffraction is greatly reduced in the far field. Source translational motion induces sound radiation in the perpendicular direction and enhances the radiated acoustic field in general. Enhancement in the forward direction is much greater than in the reverse direction.

scholarly journals A Generalized case of Electromagnetic Scattering from a finite number of Ferromagnetic cylinders

2015 ◽  
Vol 4 (3) ◽  
pp. 8 ◽  
Author(s):  
T. Kumar ◽  
N. Kalyanasundaram ◽  
B. K. Lande
Keyword(s):  
Finite Number ◽  
Electromagnetic Scattering ◽  
Scattered Field ◽  
Near Field ◽  
Scattering Problem ◽  
Normal Incidence ◽  
Generalized Solution ◽  
Numerical Results ◽  
Infinite Length ◽  
Angle Of Incidence

A generalized solution of the scattering problem from an array containing a finite number of axially magnetized ferromagnetic cylinders of infinite length placed in free space is presented in this paper. The analysis is carried out by matching the tangential boundary conditions at the surface of each cylinder to find the unknown expansion coefficients of the scattered field. Planar arrays consist of a finite number of ferromagnetic microwires are considered to obtain the numerical results for TMz and TEz polarizations in terms of the variation in scattered field components of the near field and scattering cross section (SCS) with respect to angle of incidence, radius of microwires, spacing among the microwires and operating frequency. For validation purpose, numerical results of the proposed analysis specialized for the case of single microwire and normal incidence for TMz polarization are compared with the results available in the literature for the specialized case and both are found to be matched completely.

scholarly journals Design and Study of a Wide-Band Printed Circuit Board Near-Field Probe

Electronics ◽  
2021 ◽  
Vol 10 (18) ◽  
pp. 2201 ◽  
Author(s):  
Pedro A. Martinez ◽  
Enrique A. Navarro ◽  
Jorge Victoria ◽  
Adrian Suarez ◽  
Jose Torres ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Interference ◽  
Printed Circuit Board ◽  
Transmission Loss ◽  
Near Field ◽  
Fem Simulation ◽  
Numerical Results ◽  
Circuit Board ◽  
Frequency Range ◽  
Printed Circuit

Magnetic near-field probes (NFP) represent a suitable tool to measure the magnetic field level from a small electromagnetic interference (EMI) source. This kind of antenna is useful as a magnetic field probe for pre-compliance EMC measurements or debugging tasks since the user can scan a printed circuit board (PCB) looking for locations with strong magnetic fields. When a strong H-field point is found, the designer should check the PCB layout and components placement in that area to detect if this could result in an EMI source. This contribution focuses on analyzing the performance of an easy to build and low-cost H-field NFP designed and manufactured using a standard PCB stack-up. Thereby, the frequency range and sensitivity of the NFP-PCB are analyzed through a Finite Element Method (FEM) simulation model that makes it possible to evaluate its sensibility and effective frequency range. The numerical results obtained with the FEM models are validated against measurements to verify the design and performance of our NFP. The FEM model reproduces the experimental procedure, which is used to evaluate the performance of the NFP in terms of sensitivity by means of the simulated near-field distribution. The NFP-PCB has almost a flat response from 180 MHz to 6 GHz, with an almost perfect concordance between numerical and experimental S21 results. The numerical results show an average transmission loss of −27.9 dB by considering the flat response bandwidth, whereas the experimental one is −29.7 dB. Finally, the designed NFP is compared to two high-quality commercial probes in order to analyze its performance.

Extended Kirchhoff Integral Formulations for Sound Radiation from Vibrating Cylinders in Motion

1993 ◽  
Vol 115 (3) ◽  
pp. 324-331 ◽  
Author(s):  
S. F. Wu ◽  
Z. Wang
Keyword(s):  
Acoustic Pressure ◽  
Near Field ◽  
Translational Motion ◽  
Sound Radiation ◽  
Forward Direction ◽  
Numerical Results ◽  
Rectilinear Motion ◽  
Dimensionless Frequency ◽  
Translational Speed ◽  
Kirchhoff Integral

This paper presents numerical results of sound radiation from vibrating cylinders in rectilinear motion at constant subsonic speeds by using the extended Kirchhoff integral formulations recently derived by Wu and Akay (1992). In particular, the effects of the interaction between the turbulent stress field and the vibrating surface in motion are examined. Numerical results demonstrate that this interaction is significant in the near-field when the dimensionless frequency ka > 2 and the dimensionless source translational speed M > 0.1. If this interaction is completely neglected, the predicted acoustic pressure is underestimated by as much as 10 to 20 percent in the near field. The effects of this interaction, however, decrease in the far-field. The effects of surface translational motion on the resulting sound radiation are also examined. It is found that the surface translational motion has a significant effect on the resulting sound generation in both near- and far-fields. The amplitude of the acoustic pressure is approximately doubled in the forward direction when ka > 2 and M > 0.2, which corresponds to at least a 5 dB increase in the SPL value.

Vibrations Induced by Harmonic Loadings Applied at Circular Plate on Layered Medium

2012 ◽  
Vol 29 (2) ◽  
pp. 197-206 ◽  
Author(s):  
Gin-Show Liou
Keyword(s):  
Circular Plate ◽  
Wave Equations ◽  
Layered Medium ◽  
Near Field ◽  
Three Dimensional ◽  
Ground Vibration ◽  
Numerical Results ◽  
Vibration Source ◽  
Boundary Values ◽  
Layered Stratum

AbstractA systematic procedure is developed to calculate ground vibration at any specific location in layered medium due to harmonic loadings applied at a circular plate on the medium. In the procedure, the technique decomposing the interaction tractions between excited plate and layered medium will be employed. The decomposed tractions will automatically match boundary values of general solutions of three dimensional wave equations in cylindrical coordinates. In numerical results, the effect of layered stratum on ground vibration will be investigated and how ground vibration in layered medium decreases with depth will be presented. Also, from the numerical results, one can observe ground vibration may not decay monotonically along distance away from vibration source. The presented scheme is proved to be effective and efficient for accurately predicting near-field ground response to harmonic loadings applied at a rigid circular plate on layered medium. Comments on the presented scheme and numerical results will be given.

scholarly journals Electromagnetic and transient shielding effectiveness for near-field sources

2007 ◽  
Vol 5 ◽  
pp. 57-62 ◽  
Author(s):  
C. Möller ◽  
L. Klinkenbusch
Keyword(s):  
Electric Dipole ◽  
Near Field ◽  
Numerical Results ◽  
Dipole Source ◽  
Measurement Point ◽  
Shielding Effectiveness ◽  
Field Source ◽  
Distance Vector

Abstract. The contribution deals with an investigation of the recently proposed definitions for the electromagnetic and transient shielding effectiveness (SE) in the case of an electric-dipole near-field source. To this end, new factors are introduced which depend on the distance between the dipole source and the measurement point inside the shield and which are valid for perpendicularly (with respect to the distance vector) polarized dipoles. Numerical results support and confirm the theoretical derivations.

Three-dimensional numerical simulations of dynamic faulting in a half-space

1978 ◽  
Vol 68 (3) ◽  
pp. 541-572
Author(s):  
Ralph J. Archuleta ◽  
Gerald A. Frazier
Keyword(s):  
Free Surface ◽  
Stress Relaxation ◽  
Near Field ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Circular Crack ◽  
Numerical Results ◽  
Rupture Surface ◽  
Finite Fault ◽  
Particle Velocities

abstract A method is presented for the computation of near-field particle displacements and particle velocities resulting from a dynamic propagating, stress relaxation occurring on a finite fault plane embedded within a three-dimensional semiinfinite medium. To check our numerical procedure we compare our results for a circular fault in a full space with Kostrov's (1964) analytic solution for a self-similar propagating stress relaxation. We have simulated two bilateral strike-slip earthquakes differing only in hypocentral location and examined the particle motion on the traction-free surface and on the rupture surface. Focusing of energy is evident in both ruptures. The static displacement on the rupture surface overshoots the theoretical static value by approximately 25 per cent. For the rupture that nucleated at depth the free surface almost doubled the particle velocities along the fault trace as compared with the rupture that nucleated at the free surface. Our numerical results indicate that for an earthquake occurring on a semi-circular fault with radius of 10 km, an effective stress of 100 bars and a rupture velocity of 0.9β in a medium characterized by β = 3 km/sec, α = α=3β and a density of 2.7 gm/cm3 particle velocities can reach 400 cm/sec and displacements 250 cm. We also compare our numerical results with the observations made by Archuleta and Brune (1975) for a spontaneous stress relaxation on a semi-circular crack in a prestressed foam rubber block.

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